HD 187085 b
Astrophysical Synthesis & Habitability Characterization
HD 187085 b is a confirmed gas giant exoplanet orbiting the star HD 187085, located approximately 149.7 light-years (45.9 parsecs) from the Solar System. First announced in 2006 by Anglo-Australian Telescope using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.9 Earth radii (1.24 Jupiter radii) and has a measured mass of 265.706 Earth masses (0.84 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.55 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.38 g⊕ (13.53 m/s²), and an escape velocity of 48.9 km/s.
In its orbital architecture around HD 187085, HD 187085 b completes one full revolution every 1019.74 Earth days (2.79Julian years) at a semi-major axis of 2.1 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 22.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.251, swinging from 1.5729 AU at periapsis out to 2.6271 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.900 R⊕, HD 187085 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star HD 187085 is classified as a solar-type yellow star of spectral type G0 V with an effective photospheric temperature of 6,117 K, a radius of 1.27 R☉, a mass of 1.189 M☉, an estimated bolometric luminosity of 2.026 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.747 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, HD 187085 shines at apparent V-band magnitude 7.22 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: Anglo-Australian Telescope · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 187085 |
| Spectral Type | G0 V |
| Effective Temp (Teff) | 6,117 K |
| Stellar Radius | 1.2700 R☉ |
| Stellar Mass | 1.1890 M☉ |
| Bolometric Luminosity | 2.026 L☉ |
| Metallicity [Fe/H] | 0.120 dex |
| Stellar Age | 2.747 Gyr |
| Apparent Magnitude | V: 7.220 · G: 7.075 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.100000 AU |
| Orbital Period | 1019.74 days |
| Mean Orbital Velocity | 22.4 km/s |
| Orbital Eccentricity (e) | 0.25100 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.55 g/cm³ (48.9 km/s vesc) |
| Insolation Flux | 30.5887 S⊕ (~41,631 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 149.700 LY (45.899 pc) |